1 - The officer did nothing wrong by entering the property to investigate a firearm discharge. So get off this kick about trespass because it wasn't.

2 - When the officer located you the weapon was in plain sight.

3 - While questioned you admitted that the suppressor was not licensed. Ignorance of the law is no excuse.

4 - Whether the admission can be used against you in court is something you should be discussing with a criminal defense attorney.

5 - Possessing an unregistered suppressor (silencer) is a federal crime. You can get an idea of the penalties by reviewing the following search results.

possessing an unregistered suppressor at DuckDuckGo

Your rifle is evidence of your crime. Don't count on getting it back any time soon.

Get yourself a criminal defense attorney now and see if you can get in front of this before the axe falls.